One aspect of the invention relates to an electronic structure, for example a semiconductor device, which has two or more components connected to one another by way of a number of solderable connecting elements. Aspects of the invention also relates to a method for producing such a structure.
With electronic structures such as surface-mountable semiconductor devices with a wiring substrate and solder balls as external contacts, the height of the external contacts is limited to the diameter of the solder balls. At the same time, the pitch with which the external contacts can be arranged on the underside of a semiconductor device for surface mounting on a higher-level circuit board depends on the diameter of the solder balls. Consequently, the requirement for a greater height of the external contacts because of the unfavorable aspect ratio of the solder balls can only be satisfied at the cost of a greater pitch. However, for space-saving reasons, a small pitch is desirable, because it makes a higher interconnection density possible. The height of the external contacts should therefore be made independent of the diameter of the solder balls.
A known approach to solving this is to form electrodeposited sockets with external contact areas for the solder balls. With such sockets, the height of the external contacts can be made completely independent of the diameter of the solder balls. However, with this approach, that it is technically complex and cost-intensive and does not use the wide range of inexpensive solder ball variants that are on offer in the sector of semiconductor device production.
The document 10 2005 030 946.1, which was not published before the priority date, discloses an electrical connecting element which has a socket ball and a solder ball stacked on the socket ball. The socket ball is electrically connected to a contact terminal area of the wiring substrate and has a protective coating which cannot be wetted by the solder material of the solder ball. A bounding surface of the socket ball is free of the protective coating and integrally bonded with the material of the solder ball.
With this connecting element, the protective coating of the socket ball has to be partially removed before the application of the solder ball in a single method step in order to provide a wettable bounding surface for placing on the solder ball. As a result, this solution is likewise relatively complex and consequently time- and cost-intensive.